Encapsulation of single quantum dots with mesoporous silica.

A new generation of silica encapsulated single quantum dots (QDs) was synthesized based on recent breakthroughs made in coating magnetic nanoparticles and their clusters. In comparison with the traditional Stöber sol-gel method, this new approach is significantly simpler, resulting in QDs with excellent luminescence, stability, size monodispersity, and tunable silica shell thickness. An important finding was that unlike previous reported magnetic and metallic nanoparticles, the QDs coated with only a layer of surfactant molecules were highly unstable and sensitive to the environment. As a consequence, the surfactant stabilized QDs must be prepared fresh and stored in dark before silica coating. The QDs became stable once silica shell formed on their surface and excess surfactants were removed. Further development of this technology particularly by incorporating drugs into the mesosized silica pores will open exciting opportunities in traceable delivery and controlled release of therapeutic agents.